5.08.2024

Perceptual illusion in the supermarket

Colour assimilation makes unripe oranges more appetising - confetti illusion with astonishing effects

Immature green oranges in an orange-coloured net (left) and behind a so-called "Munker net" (right). Photos: Karl R. Gegenfurtner

What has long been known in the fruit and vegetable trade is apparently based on sound science: fruit sells better if it is in a net that bears the colour of perfect specimens of its variety. This is based on a perceptual illusion known as colour assimilation or confetti illusion: objects appear to take on the colour of a pattern placed on top of them. Prof Dr Karl Gegenfurtner, perceptual psychologist at Justus Liebig University Giessen (JLU), was able to prove this in a short article in the journal "i-Perception".

The reason for the small study was his own experience of buying supposedly ripe oranges in the supermarket. Gegenfurtner only realised that the fruit actually had a greenish tinge when he got home and freed them from their orange-coloured netting. After his initial disappointment, the colour researcher's interest was piqued. To rule out the possibility that the observed effect was only due to reflections between the net and the fruit, he recreated the fruit net graphically and placed the orange behind a so-called Munker net (named after the colour researcher Hans Munker) with orange lines. Here, too, the greenish colour apparently disappears.

"I conclude from this that colour assimilation alone has a strong effect on the appearance of the colour," says Gegenfurtner. "A great joy for the colour scientist - a sad moment for the consumer!"

Version of the confetti illusion with the faces of the scientists Hermann Helmholtz, James Clerk Maxwell and Thomas Young. Graphic: Karl R. Gegenfurtner

To show how strong the underlying optical illusion can be, Gegenfurtner also demonstrated the confetti illusion with the faces of the three founders of the trichromatic colour theory (Hermann von Helmholtz, James Clerk Maxwell and Thomas Young). The effect is astonishing: depending on the stripe pattern, the neutral-coloured faces appear either garishly coloured or very dark or very light in the black and white version - even though the colour of the faces does not change.

Publication

Gegenfurtner, K.R. (2024). Perceptual ripening of oranges. i-Perception, 15(3), 1-5 https://doi.org/10.1177/20416695241258748

Further information

Prof. Dr Karl R. Gegenfurtner is a participating researcher in the Campus research focus "Mind, Brain and Behaviour". Explaining human behaviour in healthy as well as psychiatrically and neurologically ill people and understanding the functioning of the brain is the central goal of the joint research activities of the researchers in the campus focus area "Mind, Brain and Behaviour".

Contact

Justus Liebig University Giessen
Prof. Dr Karl R. Gegenfurtner
General Psychology
E-mail: gegenfurtner@uni-giessen.de